This invention relates to a motor for watercrafts and more particularly to an improved power unit and exhaust system therefor for a small watercraft powered by an inboard mounted engine.
There is a popular type of water vehicle that is intended to be driven primarily by a single driver and wherein the driver sits upon the watercraft and it is powered by an inboard mounted engine. In this type of watercraft, it is anticipated that the watercraft may tip over in use and, in fact, it is the normal practice for the driver to wear a swimming suit because of this possibility. This means that the power unit must be such that it will not be damaged by sudden maneuvering or upon tipping over.
This is particularly important in connection with the provision of the exhaust system for the engine. If the exhaust system is such that water may be drawn back into the engine through the exhaust system, severe damage to the engine might result. For this purpose, it has been proposed to provide a trap or gooseneck that connects the exhaust manifold with an expansion chamber. The expansion chamber is provided for engine exhaust cooling and silencing and the gooseneck is intended to insure against water passing back from the exhaust pipe to the engine cylinder if the boat becomes inverted. For this same reason, it has been the practice to use a forward disposed exhaust gas discharge so that the exhaust gases will be discharged from the watercraft in a generally forward location. This means that the exhaust gases must pass in a forward direction and generally along the side of the engine from the gooseneck to the area where the expansion chamber is positioned. As a result of the side by side placement of the engine and expansion chamber, the entire power unit becomes quite wide and this necessitates a widthening of the hull of the watercraft which is, of course, undesirable.
It is, therefore, a principal object of this invention to provide an improved power unit for a watercraft and more particularly to an improved high efficiency and compact exhaust system for such a watercraft.
It is a further object of this invention to provide an improved exhaust system for an inboard engine for a watercraft wherein a gooseneck and expansion chamber are incorporated so as to insure against the entry of water into the engine cylinders and which, at the same time, provides an improved and compact arrangement for the watercraft.
It is a further object of this invention to provide a power unit for a watercraft wherein the expansion chamber is located over the cylinder block and clear of the spark plugs so as to provide a larger volume expansion chamber and a compact power unit.
In connection with marine inboard engines, it is a normal practice to discharge the cooling water from the cooling jacket of the engine into the exhaust gases. With watercraft of the type heretofore described, it has been the practice to introduce this cooling water into the expansion chamber so as to cool the exhaust gases and the expansion chamber. However, the prior art methods and constructions wherein the cooling water is delivered into the expansion chamber further aggravates the likelihood of the return of water to the engine cylinders during extreme rolling operation or upon acceleration or deceleration.
It is, therefore, a still further object of this invention to provide an exhaust system for an inboard driven watercraft wherein water is precluded from re-entry into the cylinders even though it may accumulate in the exhaust expansion chamber.